1. Technical Field
The invention refers to a sliding element with one substrate and at least one layer of a sliding layer material applied to the substrate. The invention also refers to preferred applications of such sliding elements.
2. Related Art
Sliding elements such as sliding bearing elements in engines mostly consist of multiple-layer materials with especially modified surfaces, which optimize the sliding characteristics. Usually, the surfaces of sliding bearing elements are metal layers, possibly based on lead, tin or aluminium, which are applied by galvanic processes, vaporization or mechanical plating.
Furthermore, non-metal sliding layers are known having an artificial resin base, which have been modified with regard to their properties, load capacity and resistance to wear.
Although the known coatings have a relatively high load capacity, this capacity is extremely limited, such that rapid failure of the sliding function results if the load capacity limit is exceeded. The associated exposure of the substrate material, which does not have sufficient emergency operating features, then causes the total failure of the sliding bearing element due to seizure.
Resin-based sliding bearing coatings have been used for many years as a tool for the reduction of the friction in mechanical constructions. Usually, metal, plastic and rubber components are coated, which need to be permanently easily movable without further lubrication. In the typical applications the loads are rather low and the boundary conditions such as temperature and media are non-critical. It is known from various patent applications, in particular from EP 0 984 182 A1 that applications in the engine, i. e. e. g. crank shaft bearings are also possible with such sliding bearing elements. In this document, an overlay with a matrix of PI, PAI, epoxy resin or a phenolic resin is also described, to which Fe3O4 can be added, amongst others, to reduce wear.
DE 196 14 105 A1 reveals a wear- and cavitation-resistant plastics sliding layer consisting of a matrix material made of PTFE or thermoplastic fluoropolymers, Fe2O3, and solid lubricants. This material is used for bearings e. g. as a guide element for shock absorbers, and is only suitable for low sliding speeds and low loads due to its structure and the soft fluoropolymer matrix.
From EP 1 775 487 A2, a sliding bearing is known, which has a metal carrier material and an aluminium alloy and a plastic sliding layer applied to it. In order to improve the bonding strength and cavitation resistance of the plastic sliding layer, a material is suggested that has a bonding agent made of PI, PAI, PBI, EP and FP and a solid lubricant such as MoS2, graphite, PTFE and BN.